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FERRIC CHLORIDE                                    65

acidity being determined on an aliquot part   by N/io-alkali, Congo-red

paper being used as indicator,    i c.c. N/io-alkali = 0-0049 gram H2S04.

Commercial copper sulphate usually contains 98-99-5% of CuSO4 + 5H2O.

ETHER
C4H100 = 74

Colourless, light, highly volatile, neutral liquid, of peculiar odour,
D = 0-720-0722, b.pt. 35°, slightly soluble in water (10-12%) and miscible
with alcohol. Commercial ether almost always contains more or less
marked quantities of water, alcohol and free acids ; old aqueous ether may
contain hydrogen peroxide or other peroxidised compounds, which may
cause explosions when the ether evaporates. The tests to be made, besides
determinations of the density and boiling point, are as follows :

1.  Water.—When   shaken   with   aqueous   ether,   anhydrous   copper
sulphate is coloured blue, whereas if the ether is anhydrous it remains
white.   A piece of freshly cut sodium, immersed in perfectly anhydrous
ether, retains its lustre for some hours;   if the ether is wet, the sodium
becomes covered immediately with an opaque layer, while copious evolution
of hydrogen occurs.

2.  Alcohol.—10 c.c., shaken with as much water (in a closed cylinder),
should not diminish in volume by more than one-tenth ; the water separated
should not give the io do form reaction with iodine and caustic soda.

3.  Acidity.—To 20 c.c. are added io c.c. of water and a few drops of
phenolphthalein and, after shaking, the volume of standard alkali necessary
to produce a red coloration determined.    With a good sample this should
not exceed 0-1-0-2 c.c. of N/ioo-alkali.

4.  Hydrogen or other Peroxide.—0:0 c.c. are shaken in a closed
cylinder with I c.c. of I : io potassium iodide solution :  with pure ether,
no coloration should occur, even after an hour's stand in the dark.

5.  Aldehydes,  Vinyl  Products.—5  c.c.  should give no  coloration
within 5 minutes with I c.c. of water and 5 drops of Nessler reagent.

6.  Sulphur Compounds.—io c.c. are shaken with a few drops of
well cleaned mercury, which becomes brown or black in presence of sulphur
compounds.

FERRIC   CHLORIDE

FeCl3 + 6H2O = 270-22

Orange-yellow, deliquescent, crystalline masses, which may contain
oxychloride (insoluble), free chlorine and hydrochloric acid, ferrous chloride,
arsenic, nitrates and extraneous metals.

1.  Solubility.—i part of the salt and i part of water should, in absence
of oxychloride, give a clear solution which remains clear after addition of
5 vols. of alcohol.

2.  Free Chlorine and Hydrochloric Acid.—In the vessel containing
the salt are suspended a moistened starch-iodide paper and a glass rod wet

A.C.                                                                                                               5